Axial gap type generator

ABSTRACT

There is provided an axial gap type generator. The an axial gap type generator includes: generator cases are fixed to a crank case of an engine; a rotor yoke housed inside the generator cases and fixed to a crankshaft of the engine; a first stator core and a second stator core fixed to inner faces of the generator cases and disposed flanking the rotor yoke in a rotation axis direction; generator case supports for supporting the generator case in such a manner that a surface section of the generator case opposing the crank case has a spacing between the surface section and the crank case.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent ApplicationNo. 2012-009040 filed on Jan. 19, 2012, the entire contents of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an axial gap type generator that ismounted on an engine, and more particularly, to an axial gap typegenerator in which transfer of heat from the engine to a generator caseis suppressed.

2. Description of the Related Art

For general-purpose engines or the like for industrial use, there isknown a configuration in which a generator is connected with one end ofa crankshaft protruding out of an engine main body.

For instance, a technique disclosed in Japanese Unexamined PatentApplication Publication (JP-A) No. H10-4650 provides magnets for powergeneration at a flywheel that is fixed to the crankshaft end of amotorcycle engine, and coils for power generation, the coils being fixedto the engine, at sites that oppose the magnets in the radial direction.

Furthermore, in recent years, the use of an axial gap type generator hasbeen proposed for compact generator configurations. In the axial gaptype generator, stator cores that are fixed to the engine and areprovided with power generation coils, and rotor yokes that are providedwith magnets for power generation and rotate together with a crankshaftare disposed opposing one another in the center axis direction of thecrankshaft.

For instance, in an axial gap type generator disclosed in JP-A No.2009-216014, a stator core fixed to an engine is disposed in spacingbetween a pair of rotor yokes that protrude from a crankshaft towardsthe outer diameter side and are spaced apart from each other in theaxial direction.

Also, in an axial gap type generator disclosed JP-A No. 2010-038006,protrusions that are integrally formed with a stator are directlyconnected with a support member on the side of an engine, therebyenhancing the positioning precision of a stator core with respect to theengine.

When internal temperature rises, the power generation efficiency ofaxial gap type generators such as those described above drops on accountof impaired performance of magnetic bodies, and it is thereforenecessary to suppress transfer of heat, generated in the engine, towardsthe generator.

SUMMARY OF THE INVENTION

In the light of the above, it is an object of the present invention toprovide an axial gap type generator in which transfer of heat from anengine to a generator case is suppressed.

A first aspect of the present invention provides an axial gap typegenerator that includes: a generator case fixed to a crank case of anengine; a rotor yoke housed inside the generator case, and fixed to acrankshaft of the engine; and a first stator core and a second statorcore fixed to an inner face of the generator case, and disposed flankingthe rotor yoke in a rotation axis direction; a generator case supportthat supports the generator case in such a manner that a surface sectionof the generator case has a spacing between the surface section and thecrank case, the surface section opposing the crank case.

By providing a spacing between the generator case and the crank case itbecomes possible to suppress transfer of heat between the foregoing, andto prevent drops in power generation efficiency caused by risingtemperature in the interior of the generator.

Preferably, the generator case support is disposed further toward anouter diameter side than an outer peripheral edge of the stator cores.

As a result, transfer of heat towards the stator cores can be suppressedby lengthening the heat transfer path from the support to the statorcores.

Preferably, the generator case support is disposed at a position apartfrom an oil reservoir in the crank case, with the crank case viewed inthe axial direction of the crankshaft.

This suppresses transfer of heat, generated by high-temperature oil,towards the generator, across the wall face of the crank case.

Preferably, the generator case support has at least one protrusionprotruding from either one of the generator case and the crank casetowards the other.

As a result, the above-mentioned effects can be achieved withoutincreasing the number of parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional diagram of an engine that is provided withan embodiment of an axial gap type generator according to the presentinvention;

FIG. 2 is an exploded perspective-view diagram of the engine and theaxial gap type generator of FIG. 1; and

FIG. 3 is an external perspective-view diagram of a generator case ofthe axial gap type generator of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an axial gap type generator in whichtransfer of heat from an engine to a generator case is suppressed, bymounting a generator on a crank case, by way of protrusions that areformed on a front case, and by providing a spacing between the crankcase and the front case.

Embodiment

Hereinafter, an embodiment of the axial gap type generator according tothe present invention will be described.

The axial gap type generator of the embodiment is driven mounted on, forinstance, one of the ends of a crankshaft of a general-purpose enginefor industrial use.

FIG. 1 is a cross-sectional diagram of an engine provided with the axialgap type generator of the embodiment.

FIG. 2 is an exploded perspective-view diagram of the engine and theaxial gap type generator of FIG. 1.

An engine 1 in the drawings is, for instance, a single-cylinderfour-stroke OHC gasoline engine.

The engine 1 includes a crankshaft 10, a crank case 20 and so forth.

The crankshaft 10 is an output shaft of the engine 1 and is rotatablysupported on a bearing that is provided in the crank case 20.

The crankshaft 10 has, for instance, a crank pin 11, a crank arm 12, acrank weight 13 and the like at an intermediate portion thereof, and issupported on bearings on both sides.

The crankshaft 10 has output shafts 14, 15 that protrude from both sidesof the crank case 20.

The output shaft 14 drives a below-described axial gap type generator100 that is mounted on the output shaft 14.

An end face 14 a at the leading end of the output shaft 14 is formed toa planar shape that extends in a direction perpendicular to the axialdirection.

A screw hole 14 b, into which there are co-fastened a flywheel 210 andan adapter 160 that fixes a rotor yoke 150 of the axial gap typegenerator 100, is formed from the end face 14 a along the axialdirection.

The output shaft 15 is connected with an unillustrated driven device.

The crank case 20 is a container-like member that houses and rotatablysupports the intermediate portion of the crankshaft 10.

A cylinder unit of the engine 1 is integrally formed with the crank case20. A cylinder head 30 (FIG. 2) and the like is mounted at the cylinderunit. The cylinder head 30 has intake and exhaust ports, a valve train,a drive system thereof, spark plugs and so forth.

As illustrated in FIG. 1, oil O for lubricating the engine 1 is storedat the bottom in the crank case 20.

The axial gap type generator 100 is mounted on the engine 1.

The axial gap type generator 100 includes, for instance, a front case110, a rear case 120, a front stator core 130, a rear stator core 140,the rotor yoke 150, and the adapter 160.

The front case 110 and the rear case 120 are configured in the form oftwo split cases, divided in the axial direction and serve as a housing(generator case) containing the constituent members of the axial gaptype generator 100.

FIG. 3 is an external perspective-view diagram of the front case viewedfrom the crank case.

The front case 110 is integrally formed with a disc 111, a peripheralwall 112, cooling fins 113, mounting sections 114 and the like, by, forinstance, die-casting of an aluminum alloy.

The disc 111 is plate and disc shaped, and is disposed along a planethat is perpendicular to the center axis of the crankshaft 10.

An opening 111 a is formed at the central section of the disc 111. Thecrankshaft 10 is inserted through the opening 111 a.

Screw holes 111 b for fastening the front stator core 130 are formed inthe disc 111 such that they are distributed in the peripheral direction.

The peripheral wall 112 is a surface section that extends, from theouter peripheral edge of the disc 111, along the axial direction of thecrankshaft 10, towards the side opposite to the crank case 20.

The cooling fins 113 protrude in the radial direction, from the outerperipheral face of the peripheral wall 112.

The cooling fins 113 are formed in fin shapes such that they extendalong the direction of flow of cooling air that is generated by abelow-described blower fan 211. The cooling fins 113 are distributed inthe peripheral direction of the front case 110.

The cooling air flows through the spacings between the cooling fins 113towards the cylinder head 30.

The mounting sections 114 make up a generator case support thatconstitutes a base at which the front case 110 is fixed to the crankcase 20.

As an example, four mounting sections 114 are provided in FIG. 3. Thefour mounting sections 114 are distributed in the peripheral directionof the disc 111, and protrude from the outer peripheral edge of the disc111 of the front case 110 towards the outer diameter side.

The mounting sections 114 are disposed at the outer diameter side withrespect to the outer peripheral edges of the front stator core 130 andthe rear stator core 140.

Bolt holes 114 a are formed in respective mounting sections 114. Boltsfor fastening the front case 110 to the crank case 20 are insertedthrough the bolt holes 114 a.

Abutting face sections 114 b at which the mounting sections 114 abut thecrank case 20 protrude in the form of steps on the crank case 20 side ofthe disc 111.

As a result, a spacing is provided between the disc 111 and the crankcase 20 upon fastening of the front case 110 to the crank case 20.

Connection sites for connecting the mounting sections 114 and the crankcase 20 are disposed apart from the area at which high-temperature oil Ois stored, with the crank case 20 viewed in the axial direction of thecrankshaft 10.

The rear case 120 is disposed on the side opposite to the crank case 20,across the front case 110.

The rear case 120 is integrally formed with a disc 121, a peripheralwall 122, cooling fins 123 and the like, by, for instance, die-castingof an aluminum alloy.

The disc 121 is plate and disc shaped, and is disposed along a planethat is perpendicular to the center axis of the crankshaft 10.

An opening is formed at the central section of the disc 121. The adapter160 is inserted through this opening. The opening is formedsubstantially in the same way as the opening 111 a of the front case110.

Screw holes for fastening the rear stator core 140 are formed in thedisc 121 such that they are distributed in the peripheral direction.These screw holes are formed substantially in the same way as the screwholes 111 b of the front case 110.

The peripheral wall 122 is a surface section that extends, from theouter peripheral edge of the disc 121, along the axial direction of thecrankshaft 10, towards the crank case 20 (towards the front case 110).

The peripheral wall 112 of the front case 110 and the peripheral wall122 of the rear case 120 are joined in a state where the leading endedges of the peripheral walls abut each other, and are fastened by wayof bolts or the like.

In order to enhance the relative alignment precision between the frontcase 110 and the rear case 120, portions of the leading end of theperipheral wall 112 on the inner diameter side of the front case 110protrudes, in the form of a step towards the rear case 120, while at theleading end of the peripheral wall 122 there are formed stepped recessesonto which these protrusions fit.

The front case 110 and the rear case 120 are positioned through aso-called “socket-and-spigot joint” such that the protrusions of theperipheral wall 112 fit onto the recesses of the peripheral wall 122.

The cooling fins 123 protrude in the radial direction from the outerperipheral face of the peripheral wall 122.

The cooling fins 123 are formed substantially in the same way as thecooling fins 113 of the front case 110 described above.

The cooling fins 113 and the cooling fins 123 are disposed atoverlapping positions in the peripheral direction of the axial gap typegenerator 100, and are formed so as to configure a substantiallycontinuous surface section.

Power generation coils are provided at the front stator core 130 and therear stator core 140 The Power generation coils are configured by, forexample, winding coils around an iron core.

The front stator core 130 is mounted on the surface section on the rearcase 120 side of the disc 111 of the front case 110.

The rear stator core 140 is mounted on the surface section on the frontcase 110 side of the disc 121 of the rear case 120.

The front stator core 130 and the rear stator core 140 are formed splitinto a plurality of pieces in the peripheral direction, such that thepieces are fastened to a respective discs 111 and 121 by way of screws.

The front stator core 130 and the rear stator core 140 are disposedopposing each other in the axial direction of the crankshaft 10.

The rotor yoke 150 is configured through mounting of permanent magnets151 for power generation on both sides of a disc-like member that has anopening in the central section.

The rotor yoke 150 is disposed between the front stator core 130 and therear stator core 140, with a predetermined gap left between the statorcores.

The rotor yoke 150 is fixed to the crankshaft 10 by way of thebelow-described adapter 160, and rotates relatively with respect to thestator cores 130 and 140 during operation of the engine 1.

The adapter 160 is fixed to the output shaft 14 of the crankshaft 10,and the rotor yoke 150 is fixed to the adapter 160.

The adapter 160 is integrally formed with a disc 161, a tubular section162, a shim clamper 163 and a flywheel mounting section 164.

The inner diameter-side portion of the rotor yoke 150 is fastened to theouter diameter-side portion of the disc 161. The disc 161 is plate anddisc shaped.

The disc 161 is disposed inside the rear case 120, and is provided suchthat the position of the disc 161 in the axial direction of thecrankshaft 10 is in the vicinity of the leading end of the output shaft14.

The rotor yoke 150 is mounted on the surface section on the crank case20 side of the disc 161.

The tubular section 162 is cylinder shaped and protrudes from thesurface section on the crank case 20 side of the disc 161. The outputshaft 14 of the crankshaft 10 is inserted into the tubular section 162.

The shim clamper 163 is a surface section that forms a bottom face ofthe tubular section 162, and is plane shaped in a directionperpendicular to the rotation axis direction of the crankshaft 10.

A disc-like shim S for adjusting the axial-direction position of therotor yoke 150 is clamped between the shim clamper 163 and the end face14 a of the output shaft 14 of the crankshaft 10.

The thickness of the shim S is set in such a manner that the rotor yoke150 is disposed so as to leave appropriate gaps with respect to thefront stator core 130 and the rear stator core 140.

Specifically, for instance, the distance, in the axial direction of thecrankshaft 10, between the end face 14 a of the output shaft 14 and asite for measurement is measured, the site being set beforehand at thecrank case 20 or at a member fixed thereto. A shim is selected that hasa thickness corresponding to the measured distance, on the basis ofprepared correlation data of distance-shim thickness.

The flywheel mounting section 164 is shaped as a tapered shaft andprotrudes from the disc 161 to the side opposite to the crank case 20.

The flywheel 210 of the engine 1 is mounted on the flywheel mountingsection 164.

As illustrated in FIG. 1, the flywheel 210 and the adapter 160 areco-fastened and fixed to the crankshaft 10 with a high-tension bolt B.

Connection strength can be secured easily by thus configuring theflywheel mounting section 164 in the shape of a tapered shaft.

The blower fan 211 that generates cooling air during rotation isintegrally formed with the flywheel 210.

The flywheel 210 is provided with a blower housing base 220 and a blowerhousing 230 respectively on the crank case 20 side and on the oppositeside of the crank case 20.

The blower housing base 220 and the blower housing 230 are fixed to therear case 120 and are disposed surrounding the flywheel 210, includingthe blower fan 211. The blower housing base 220 and the blower housing230 form an air flow path in which cooling air passes by the coolingfins 113 and 123 and reaches the cylinder and the cylinder head 30.

The embodiment explained above elicits the following effects.

(1) By supporting the disc 111 apart from the crank case 20 with themounting sections 114 which protrudes from the disc 111 of the frontcase 100, transfer of heat between the foregoing can be suppressed, andpower generation efficiency can be prevented from decreasing due to thetemperature rise in the interior of the axial gap type generator 100.

Furthermore, integral formation of the mounting sections 114 with thefront case 110 achieves the above-described effect without increasingthe number of parts.

(2) Since the heat transfer path from the crank case 20 to the statorcores 130 and 140 is lengthen by arranging the mounting sections 114 onthe outer diameter-side against the stator cores 130 and 140, heattransfer to the stator cores 130 and 140 can be suppressed.

(3) Transfer of heat from the oil O to the axial gap type generator canbe suppressed by disposing the mounting sections 114 at positions otherthat the oil reservoir in the crank case 20.

Variations

The present invention is not limited to the embodiment explained above,and may accommodate various alterations and modifications, which liewithin the technical scope of the present invention.

The shape, structure, material, manufacturing method, disposition and soforth of the members that constitute the engine and the axial gap typegenerator are not limited to those in the configuration of theabove-described embodiment, and can be appropriately altered.

In the present embodiment, for instance, the mounting sections providedon the generator case side protrude towards the crank case.Alternatively, crank case-side mounting sections may be caused toprotrude towards the generator case alternatively or with the mountingsections still being protruded towards the crank case.

A spacer comprising a separate part may be provided between thegenerator case and the crank case. In such an instance, the spacer maybe made with a material having low heat conductivity with respect to thecrank case and the generator case, such as a nylon resin.

What is claimed is:
 1. An axial gap type generator comprising: agenerator case fixed to a crank case of an engine; a rotor yoke housedinside the generator case and fixed to a crankshaft of the engine; afirst stator core and a second stator core fixed to an inner face of thegenerator case and disposed flanking the rotor yoke in a rotation axisdirection, a generator case support that supports the generator case insuch a manner that a surface section of the generator case opposing thecrank case has a spacing between the surface section and the crank case.2. The axial gap type generator according to claim 1, wherein thegenerator case support is disposed further toward an outer diameter sidethan an outer peripheral edge of the stator cores.
 3. The axial gap typegenerator according to claim 1, wherein the generator case support isdisposed at a position apart from an oil reservoir in the crank case,with the crank case viewed in the axial direction of the crankshaft. 4.The axial gap type generator according to claim 1, wherein the generatorcase support has at least one protrusion formed protruding from eitherone of the generator case and the crank case towards the other one.